... increasingly seen as critical for making Earth so favorable to complex life. Among them are
these:
*An orbit that keeps a planet at exactly the right distance from its star to ensure that water
remains liquid, not vapor or ice.
*A large moon at just the right distance to minimize changes in a planet ...

... 20. The name of our star
system.
23. Anything that orbits a larger
body.
24. Most massive planet.
25. The time it takes Luna to
make one complete revolution
AND rotation.
28. The shape of our galaxy
when viewed from above.
29. Different moon ____ occur
because of the moon's location
relative to the ...

... from the sun and the direct angle of sunlight hitting the area. Also caused
by revolution.
6. Lunar – Moon – natural satellite – moon cycle is about 28 days long. Moon
means month. Be able to identify phases of moon
7. Solar – sun – only average size star in our solar system that gives us light
and ...

... It’s named after the Roman goddess of love and beauty. It’s the only
planet named after a female.
It has no moons or rings
Unlike most other planets, it rotates clockwise (retrograde rotation).
Billions of years ago its climate may have been similar to Earth
One day on Venus is longer than one year ...

... Requirements for the star
• Solar like Main Sequence star, stable for
billions of years
• Less than 1.5 times massive than the
Sun; otherwise too much UV
• More than 0.3 times the mass of the Sun;
large warm region near the star for liquid
water
• Limited to no more than 10 billion stars
...

Rare Earth hypothesis

In planetary astronomy and astrobiology, the Rare Earth Hypothesis argues that the origin of life and the evolution of biological complexity such as sexually reproducing, multicellular organisms on Earth (and, subsequently, human intelligence) required an improbable combination of astrophysical and geological events and circumstances. The hypothesis argues that complex extraterrestrial life is a very improbable phenomenon and likely to be extremely rare. The term ""Rare Earth"" originates from Rare Earth: Why Complex Life Is Uncommon in the Universe (2000), a book by Peter Ward, a geologist and paleontologist, and Donald E. Brownlee, an astronomer and astrobiologist, both faculty members at the University of Washington.An alternative view point was argued by Carl Sagan and Frank Drake, among others. It holds that Earth is a typical rocky planet in a typical planetary system, located in a non-exceptional region of a common barred-spiral galaxy. Given the principle of mediocrity (also called the Copernican principle), it is probable that the universe teems with complex life. Ward and Brownlee argue to the contrary: that planets, planetary systems, and galactic regions that are as friendly to complex life as are the Earth, the Solar System, and our region of the Milky Way are very rare.